"My choreographer actually, when I was doing the rehearsals for this video, he was like, 'Britney, you are not a sweet mommy in this video. You are nasty bitch mommy in this video,'" the pop star said in an exclusive sit-down with E! News' Catt Sadler in her dressing room at the iHeartMusic Radio Festival in Las Vegas on Saturday.

"And I was like, 'OK...OK!" Britney gasped, her eyes growing wide as she imitated herself reacting to being told she had to get down and dirty.

"When you start to feel the charcter, you start to feel silly, 'cause you're like, 'This isn't me, I'm not like all like this,'" Britney explained, "moving all sexually and stuff like that, so as 'mommy' you feel really awkward doing that."

But "once you get out there and the camera starts rolling, you just kind of feel it out and you do it. But when I watch playbacks sometimes, I'm like, 'Who do I think I am?! Who the hell do I think I am?!'"

You're Britney, bitch!

And now she's bringing her talents to Las Vegas, to start a two-year concert residency at Planet Hollywood in December.

Jennifer Cooper

"It seemed like the ideal job to me because I felt like when I was on tour, I'm in a different bed every night..."It felt kind of ideal to be set in one place," the mother of two told Catt, adding that Vegas will probably be a "second home," not her primary residence.

Asked what sort of theatrics she has planned, Britney said, "The shows here are so incredible, I really want to bring my goods to the table."

Speaking of her goods, the 32-year-old singer joked about heading into rehearsals, "I'm gonna shed 30 pounds next week!"

But there really is no big secret as to how Britney has been maintaining that slammin' bod of hers lately: Moderation.

"I ate six times today, so I'm not always diligent with the food because I love food," the singer said. "It's really hard [to cut down] but you know, you have to do it.

"I feel better though when I'm lighter, I do," she added. "My spirits are higher...but it 's just, you love pizza sometimes. It just sucks, man—it sucks."

Britney was at the iHeartRadio fest to introduce new pal Miley Cyrus, who she recently recorded a song with for Miley's upcoming new album, Bangerz.

"My manager [Larry Rudolph] is her manager and she's been working on her album lately and I've been working on an album, so we hit the studio together a lot, and she's a cool girl," Britney described her fellow star.

Watch the clip to hear what else Britney revealed and see more highlights from the iHeartRadio Music Festival tonight on E! News at 7 p.m. & 11:30 p.m.